In the conventional manufacture of bricks, unfired and pliable clay is extruded continuously into an elongated column which is cut transversely into a series of column slugs. Typically, each column slug is pushed transversely through a plurality of evenly spaced cutting wires to form individual green bricks. The green bricks are separated, conveyed to and set on cars, moved into drying ovens, transferred to a kiln and fired.
Prior art brick cutting methods are satisfactory for only those applications where some brick edge and face defects are acceptable. Cutting a column slug into green bricks by simply pushing cutting wires through the clay (without prior notching along the intended cutting lines) produces sharp uneven edges and burrs of clay. It also produces lugs on the edges where the cutting wires are leaving the brick. These lugs are aesthetically unacceptable and especially conducive to breaking and chipping. Stacking on kiln cars, coupled with the normal rocking and jostling encountered during cart movement, virtually guarantees chipping of abutting brick edges of many bricks. Lug and chipping defects result in rejection of a significant percentage of finished bricks.
One attempt to cure such conventional brick cutting procedures is disclosed in U.S. Pat. Nos. 3,350,757 and 3,461,196 to Bowles. Here, in a first embodiment (FIGS. 1-4) clay bars (slugs) cut from an extruded clay column are conveyed to a first station. Opposing sets of vertically-mounted wedge-shaped knife blades are simultaneously pressed into two opposing sides of the clay slug to form vertical grooves or notches in these sides of the slug along intended cutting lines. The blades are retracted, and the slug is conveyed to a second station where a "pusher" block contacts one side of the vertically-notched slug and pushes it toward a cutting station. Vertical wires are aligned with vertical notches in the column slug and a corresponding roller is mounted along a shaft in front of each wire with its planes of rotation aligned with its corresponding cutting wire. As the pusher block forces the column slug through the cutting assembly, each roller forms (in advance of the cutting wire) a horizontal notch or groove on the top surface of the column slug that is aligned with a corresponding vertically-formed notch. The cutting wires, positioned directly behind corresponding rollers, traversely cut the column slug through the troughs of the notches to form individual green bricks. In a second Bowles embodiment (FIGS. 5-8), the brick cutting wires are horizontally disposed and the slug is pushed upward through the wires to cut individual bricks. A notch-forming roller is aligned with each wire at each side of the slug as to make vertical notches prior to cutting. The same rollers form a horizontal notch on the top side of the slug as it is being laterally transferred into the cutting station.
While the Bowles three-side notching methods are an improvement over conventional methods, they suffer from a number of problems. First, the notching and cutting operation requires transfer of the slug to plural process stations and/or use of different notching apparatus. For example, in the first Bowles embodiment, after the column slug is transferred to the first station and vertically notched, it must be moved again to the second station and carefully aligned with respect to the wire/disk cutting assembly to ensure alignment with and cutting along the vertical notches.
High brick manufacturing capacities make proper alignment extremely difficult to achieve in the Bowles system. Vertical and horizontal notches inevitably become misaligned, resulting in bricks which are unacceptable aesthetically. Additionally, pushing the bricks through rollers and wires in the second station causes lugs to be pulled at brick edges where rollers and wires leave the cut slug. Again, this is not acceptable. Moreover, the second Bowles embodiment does not allow notching of the bottom of the slug, and therefore, similar lugs are pulled at the edges of the brick.
Another attempted solution is disclosed in German Patent DE-AS*2,832,167--Borgmann. The Borgmann device features a roller assembly with an upper and a lower row of notching rollers positioned in the same vertical plane. A pushing block delivers the column slug to a first position where the roller assembly can initially contact the front surface of the slug. The retracted roller assembly is then extended vertically across the front vertical face of the slug and in the process forms a plurality of parallel notches. When the roller assembly is fully extended, the pushing mechanism forces the column slug between the upper and lower set of rollers to form parallel transverse notches along the top and bottom surfaces of the slug. The column slug is then stopped at a second position where the roller assembly contacts the rear vertical face of the column slug. The roller assembly is then retracted thereby forming a second vertical notch on the rear face of the slug. In this manner, all four sides of the slug are notched prior to brick cutting.
Although an improvement over the Bowles system, the Borgmann device has a number of drawbacks. For example, because of the inertia of the clay column slug, it is difficult to accurately and uniformly always position the entire length of the slug at exactly the same transverse position relative to the roller assembly. Consequently, when the roller assembly is extended across the front and rear vertical faces of the slug, notches of irregular depth may be formed from one cycle to the next when the front notches are compared to the rear notches. If one end of the slug is positioned slightly forward of the preferred position, for example, the depth of the vertical notch may be greater at the forward end of the slug than at the rear end.
The frictional resistance between the bottom of the slug and the conveyor varies along the slug length. As a result, when the upper row of Borgmann rollers is moved down along the rear vertical slug face, portions of the slug may move in low friction areas pushing those portions away from the rollers resulting in shallow, inconsistent notch depth. Furthermore, when the upper and lower rows of Borgmann rollers notch the top and bottom surfaces of the column slug, respectively, clay material is displaced in the direction where the rollers leave the slug, so that lugs are formed, which are not acceptable aesthetically.
Accordingly, there is still need for a brick handling system which more efficiently and effectively provides more uniformly cut bricks without lugs on their edges. In addition, it is desirable that the notching and cutting operations take place at a single work station using a single piece of equipment.